Answers

Yes, they CAN delete their answer at any time until YOU choose a best answer, with ONE exception. You do NOT have the option to delete your answer in the MOBILE format if your cellphone is NOT a smart phone. The phone does not have the lower or band width. It is a limitation of the phone. I don't know about rablets.

Yes. They don't lose the ability to delete their answer until you select a Best Answer for the question.

However, other reasons an answer might disappear' before you can read it are because it was reported and removed or because it's caught in the spam filter and visible only to the user who posted it (you may be able to see in Notifications that you have an answer, but it won't show up when you go to your question)